1. The Field of the Invention
The present invention relates to surgical lasers and, more particularly, to a disposable hand piece which carries the optical fiber and electrical switching element of a surgical laser.
2. The Prior Art
Although the theory behind lasers was first described by Einstein in the early 1900s, it was not until several decades later that significant breakthroughs were made in their development. Early lasers utilized solid crystalline rods constructed, for example, from ruby. Such lasers were generally only capable of giving short bursts of light. In about 1958, scientists developed a process whereby laser light could be obtained by exciting various gases within a tube. This was a significant breakthrough since it meant that a continuous laser beam could be produced.
The advent of the laser has opened new frontiers to many areas of science and has revolutionized many procedures. One of the most important of these new frontiers has been the application of laser technology to various procedures in the field of medicine. The first significant medical use of a laser occurred in 1965 when doctors utilized an argon laser to repair a detached retina. The doctors were able to focus the laser into the interior portion of an eyeball and "weld" the detached retina back into place. Since that time, different types of lasers have been developed and applied to numerous surgical procedures.
For purposes of surgery, lasers operate on the principle that the highly collimated laser light beam may be converted into thermal energy when focused upon tissue. Because lasers can be focused onto very small areas, it is possible to be extremely precise during certain operations and to treat specific pathologies without affecting surrounding tissue. Each type of laser produces a light beam having a specific and unique wave length. Inasmuch as different wave lengths of light are absorbed, reflected, scattered, or transmitted by tissue to varying degrees, each type of laser has been found to have unique applications.
For example, argon lasers produce a visible blue-green light having a wavelength in the 488 to 514 nanometer range. This light is easily transmitted through clear aqueous tissues such as the cornea, lens and vitreous humor of the eye. On the other hand, certain tissue pigments such as melanin and hemoglobin absorb this light very effectively. Therefore, argon lasers have proven to be very effective in treating pigmented lesions such as port-wine hemangiomas. The laser light passes through the skin surface without being absorbed significantly until it reaches the pigmented layer where it is almost totally absorbed, causing heat generation and protein coagulation.
The argon laser can also effectively be utilized as a scalpel. By focusing the laser to a narrow beam or by increasing its intensity, the power density can be increased to a strength sufficient to vaporize the target tissue, thus allowing incisions to be made. Additionally, because the argon-produced light is readily absorbed by hemoglobin, severed blood vessels are coagulated simultaneously with the formation of the incision.
A second type of laser which has found significant use in the medical field is the carbon dioxide (CO.sub.2) laser. The CO.sub.2 laser produces invisible infrared light with a wave length of about 10,600 nanometers. This light is entirely absorbed by the water present in body tissues within about 100 microns of the point of impact. However, because of this efficient absorption, CO.sub.2 lasers make effective scalpels but must be used in dry, non-bleeding areas to prevent the energy from being dispersed. Because the CO.sub.2 light beam is so readily absorbed, it cannot be used when it is necessary to transmit the light through various layers of tissue to reach the pathology.
Other types of lasers which have been utilized in surgical procedures include the neodymium yttrium aluminum garnet (Nd-YAG) and xenon lasers. Each of these lasers also has its preferred applications.
Some laser beams such as those of the argon, Nd-YAG, and xenon lasers can be transmitted through optical fibers to the point of application. On the other hand, because the CO.sub.2 laser has a relatively large wavelength, it cannot be transmitted through these optical fibers but must be directed through multi-jointed arms containing lenses and mirrors, and is thus limited to line of sight operations. Additionally, the multi-jointed arms with their accompanying lenses and mirrors are complicated and expensive to construct. Accordingly, argon type lasers are more convenient to use and they have found a wide variety of applications in the medical field.
The optical fiber (typically quartz) used to transmit an argon-type laser beam may be extremely small, generally ranging from about 0.1 to about 0.6 millimeters in diameter, and is quite fragile. Accordingly, the fiber is usually encased within a silicon sheath and is then placed within some type of protective plastic tubing. The entire assembly is sometimes referred to as a "laser catheter."
In the past, it has been common practice for surgeons to simply grasp the protective tubing when using an argon type laser in surgical procedures. This may create some difficulties because the tube is very flexible and long, and is thus difficult to control with a high degree of precision. Moreover, because the optical fiber is sometimes very small, the overall protective tubing may also be correspondingly small in size and thus, difficult to grasp near the tip when attempting to position the tip of the optical fiber with precision.
Another common problem in the state of the art is that argon type medical lasers typically do not have a convenient means for switching the laser on and off. A small amount of light is generally constantly transmitted through the optical fiber for purposes of assisting the surgeon to accurately aim the laser beam. However, because of the extreme power of the laser beam, it is imperative that full power only be applied at the precise instant that the surgeon desires to perform the surgical procedure. Normally, full laser power is controlled by a foot switch connected to the laser source.
The use of a foot switch for purposes of turning the laser beam on and off gives rise to several disadvantages. First, the surgeon must be very careful that he does not accidentally activate the foot switch. Second, in many types of operations the surgeon will be required to operate over substantial periods of time, which will mean repeated activation and deactivation of the laser foot switch. During this type of extended operation, the surgeon may become extremely uncomfortable or fatigued by virtue of the fact that he must constantly keep one foot resting on the foot switch, which prevents him from putting his full weight on that foot. Obviously, this may adversely affect the surgeon's balance, rendering his job more difficult. Moreover, if the surgeon completely removes his foot from the foot switch, the switch may become displaced and he may have difficulty locating it once it is desired to again activate the laser beam. This is especially disadvantageous should the surgeon unexpectedly need to utilize the laser beam to coagulate bleeding vessels. Finally, it is also difficult to control the foot switch, especially when wearing shoes. Use of a foot switch also renders it more difficult for the surgeon to accurately place a laser beam and requires additional hand and foot coordination, which greatly increases the difficulty of the surgical procedure.
Accordingly, what is needed in the art is a hand piece which can be attached to the end of a laser catheter assembly so as to provide the surgeon with a convenient tool which he can easily grasp and which he can more easily and more precisely use for purposes of positioning the tip of the optical fiber, and which includes means for activating or deactivating by hand the laser beam supplied through the catheter assembly.